Doctor blade mechanism



April 21, 1970 M. J. FUERST DOCTOR BLADE MECHANISM 2 Sheets-Sheet lFiled May 23, 1966 April 21, 1970 M. J. FUERST DOCTOR BLADE MECHANISM 2Sheets-Sheet 2 Filed May 23, 1966 United States Patent l 3,507,745DOCTOR BLADE MECHANISM Milton J. Fuerst, New London, Wis., assignor toKimberly-Clark Corporation, Neenah, Wis., a corporation of DelawareFiled May 23, 1966, Ser. No. 558,536 Int. Cl. B31f 1/12; D21g 3/04 US.Cl. 162-281 1 Claim ABSTRACT OF THE DISCLOSURE My invention relates topapermaking machines and more particularly to apparatus for makingdifferentially creped tissue sheets which are tissue sheets having aseries of finely creped strips separated by relatively coarsely crepedstrips.

It has been proposed to make such differentially creped tissue sheets inVoigtman et a1. Patent No. 3,017,317, by spraying the drier drum for thetissue with spaced jets of liquid release agent, and it has beenproposed to make such sheets in Nobbe Patent No. 3,163,575, by means ofa creping doctor blade effective on a drier drum. The Nobbe doctor bladehas an end surface which extends at an obtuse angle with respect to thetrailing end of the tangent to the drier drum at the place of contact ofthe blade, and notches are cut in the blade to provide surfacesextending at an acute angle with respect to this end of the tangent. Thefirst mentioned blade surfaces finely crepe paper tissue from the drierdrum, and the surfaces in the blade formed by the notches flare orcoarsely crepe the tissue from the drum so as to provide a compositetissue which has alternate finely creped and coarsely crepedlongitudinal strips.

It is an object of the present invention to provide an improved,simplified doctor blade of this general type which has alternate crepingend surfaces extending at different angles with respect to the surfaceof the drier drum along a substantial line of contact of the blade withthe drum; and more particularly it is an object to provide such a doctorblade which, except for spaced edge portions that have been blunted, hasan edge portion extending at an acute angle with respect to the trailingend of the tangent to the drier drum at said substantial line ofcontact. It is a further object of the invention to provide a simplifiedmethod for making such a doctor blade.

The invention consists of the novel constructions and methods to behereinafter described and claimed for carrying out the above statedobjects, and such other objects, as will be apparent from the followingdescription of a preferred form of the invention, illustrated withreference to the accompanying drawings, wherein:

FIG. 1 is a side elevational view of the drier end of a papermakingmachine including a Yankee drier drum and a doctor blade for crepingpaper from the drum;

FIG. 2 is a fragmentary sectional view of the doctor blade and thedoctor blade supporting assembly;

FIG. 3 is a perspective view of the creping edge of the doctor bladeprior to run-in of the blade on the surface of the drier drum;

FIG. 4 is a fragmentary cross-sectional view of the doctor blade takenon line 44 of FIG. 3;

FIG. 5 is a sectional view similar to FIG. 4 and taken on line 5-5 ofFIG. 3;

ice

FIG. 6 is a view similar to FIG. 5 after the blade has been run in onthe surface of a rotating drier drum to put it into operating condition;

FIG. 7 is a fragmentary end view of the doctor blade in creping positionon the Yankee drier drum; and,

FIG. 8 is a side elevational view of the doctor blade showing the mannerin which a toothed gear may be run back and forth on the sharpened edgeof the blade for the purpose of providing notches in the sharpened edgeso as to give the blade its differential creping capability.

Like characters of reference designate like parts in the several views.

Referring now to FIG. 1, in particular, the papermaking machinefragmentarily illustrated includes a drier drum 10 which is supported bya frame 11 disposed on a suitable foundation 12. The wet paper web 13,in the operation of the machine, is applied on the outer surface of thedrum and is dried by the drum during less than a single revolutionthereof.

The drum comprises a cylindrical shell 14 fixed to heads 15, and theheads and shell may be made of cast iron, for example. The drum ismounted for rotation by means of end shafts 16 disposed in bearings 17secured to the frame 11 and is driven by conventional driving mechanism(not shown) attached to one of the shafts 16, Steam is applied to thedrum 10 by conventional connections for heating the drum to dry the web13, and a heated hood 18 extends around the upper portion of the drum 10for providing additional heat for drying the web. The hood is providedwith suitable hot air inlets and outlets for the entrance and dischargeof the heated air or other medium.

The paper web to be dried is carried by an endless felt 19 which extendsaround a pressure roll 20 suitably mounted so as to force the felt 19against the outer surface of the drum 10, whereby the web 13 transfersfrom the felt to the drum.

A creping doctor assembly 21 is utilized for creping the paper web fromthe surface of the drum 10. The assembly comprises a doctor blade holder22 suitably carried and fixed within the assembly 21 and a crepingdoctor blade 23 secured in the holder.

The doctor blade holder, referring particularly to FIG. 2, may be seento comprise side support bars 24 and 25 on opposite sides of the blade23. A support bar 26 is disposed between the bars 24 and 25; and thebars 24, 25 and 26 are fastened together at their bases by any suitablemeans (not shown) to act as a single assembly. The doctor blade 23extends slightly beyond the ends of the drum 10 and is substantiallycoincidental in length with the bars 24, 25 and 26.

Three backing blades 27, 28 and 29 are provided behind the doctor blade23 for supporting the blade. The backing blades are fixed at their baseswith respect to the bars 24 and 25 by any suitable means (not shown).The bar 24 has a guard portion 30 fixed to it, and the end 30a of theguard portion is disposed somewhat downwardly with respect to the edgesof the backing blades 27, 28 and 29.

Prior to run-in on the moving peripheral surface of the drum 10, thedoctor blade 23 appears in the condition shown in FIGS. 3, 4 and 5. Theblade is ground or otherwise formed with a surface or side 23a that isat an acute angle a with respect to the side or base surface 23b of theblade. Thin notches 31 are provided on the edge of the blade at whichthe surfaces 23a and 23b meet, and the bottoms of the notches 31 areformed by surfaces 230 each of which extends at a larger angle b withrespect to the face or base surface 23b of the blade.

Spring steel, for example, which is flexible has been found suitable asmaterial for the blade 23. The blade 23 may vary in thicknessconsiderably; for example, the thickness for very satisfactory operationmay well be between .025 inch to .050 inch. The blade is initiallyformed so that the surface 23a extends for the complete length of theblade and intersects the surface 23b in a knife edge 23d for thecomplete length of the blade. As the blade is actually used, it isprovided with the notches 31, and these may be formed by filing them inthe blade, for example, or they may also be formed simply by rolling agear 32 having teeth 33 (see FIG. 8) on its periphery back and forthalong the sharp edge 23d until the notches 31 are formed to the desireddepth. The notches may, for example, have a width on their base surfaces23c of about .005 inch, and the depth of the notches may also be about.005 inch but may Well vary from about .0015 inch to .007 inch. Theteeth 33 havea rolling contact wiith spaced portions of the edge 23d anddull the edge in the portions thereof contacted by the teeth 33 in orderto provide the notches 31. I have found that creping is facilitated ifthe surfaces 23c are somewhat rough. This roughness may be attained ifthe ends of the teeth 33 are provided with surfaces which are like theabrading surfaces of a file; and, in fact, file segments may be fixed onthe end of the teeth 33 for this purpose. Such file segments may, forexample, be parts of fine files of the type used for dressing thedistributor contacts of the ignition system for an internal combustionengine and may, for example, have about 80 ridges and grooves per inchof file length.

In order to put the blade 23 in condition for differential creping, itshould first be run in and preferably dressed before running in.Dressing is done by moving a stone or file along the blade surface 23bto remove any burrs protruding on this surface due to the dulling actionof the gear teeth 33 on the sharpened edge of the blade 23. The blade 23is run in by running it on the surface of the drier, preferably withouta sheet 13 being provided on the felt 19 and drier. This has the effectof wearing the edge surfaces of the blade 23 in contacts with the drumso that the edge surfaces now appear as seen in FIG. 6. After suchrunning in, the end of the blade 23 is in the shape of a short are 23corresponding to the cylindrical shape of the drum 13, and this arcterminates at an edge 23 on the surface 23a and at edges 23g on thesurfaces 230. Thus, after such run-in, the surface 23a, which is at anacute angle a with respect to the base surface 23b of the blade 23 andalso the surface 230, which is at a larger angle b with respect to thebase surface 2317, are both in contact and thus in creping relation withrespect to the outer surface of the drum 13.

In operation, the doctor blade may be disposed at various angles withrespect to a tangent 34 (see FIG. 7) to the drum 10 at the edge 23 incontact with the drum. The angle c of the blade 23, noting the directionof drum rotation A and measuring from the trailing end of the tangent34, for satisfactory operation may be, for example, from 20 to 45.

The surface 23a is a flaring or coarsely creping surface and thesurfaces 230 are finely creping surfaces with respect to the surface ofthe drum 10 after run-in. The surface 23a extends at an acute angle d(which is the sum of the angles a and c) with respect to the trailingend of the tangent 34, and the angle a. is preferably 40 to 75. Thesurface 230 extends at a larger angle e (which is the sum of the anglesb and c) with respect to the trailing end of the tangent 34, and theangle e is preferably 85 to 150. It will be noted that the angle e canthus be a. relatively large acute angle or an obtuse angle, as desired.Assuming that the angle 0 is 30", for example, the angle a defining theangle of the surfaces 23a with respect to the base surface 23b of thedoctor blade 23 thus is an acute angle of 10 to 45, and the angle bbetween the surfaces 230 and the base surface 23b of the blade 23 is anangle of to The surfaces 23a and their creping edges 23 will strip orflare off the tissue web 13 from the surface of the drier drum 10 withvery little or coarse creping, while the surfaces 230 with their edges23g will finely crepe the web 13 from the drier drum due to the factthat the web tends to double back on itself and become crinkled as theweb strikes the surfaces 230 that either lean toward the leading end ofthe tangent 34 or else extend substantially directly outwardly, ornearly at right angles, with respect to the tangent 34. Thus, thecreping blade of the invention produces a differentially or unevenlycreped product or tissue, such as the product described in No-bbe PatentNo. 3,163,575, and also, incidentally, described in Voigtman et al.Patent No. 3,017,317. The advantageous and usages of thesedifferentially creped Webs or sheets are very suitable for thesepatents, and, as it set forth in these patents, such differenttiallycreped webs or sheets are very suitable for cushioning and insulatingpurposes.

It will be apparent that the length and spacing of the notches 31 may bevaried as desired in order to change the differential creping action.The notches 31 may, for example, be about inch long, and the spacingbetween the notches may also be approximately the same.

The creping doctor blade above described affords an economical mechanismfor producing the differentially creped tissue disclosed in the abovementioned Patents 3,017,317 and 3,163,575, without the necessity ofusing relatively expensive chemical solutions or without the relativelycostly necessity of grinding notches in a doctor blade. Inasmuch as thedoctor blade disclosed herein is simply one that initially has itscomplete side sharpened with the acutely extending surface 23a and sharpedge 23d, and with the edge 23d subsequently being blunted and dulled inselected spaced portions, the blade may be constructed very economicallywhile yet obtaining the desired differential creping results.

What is claimed is:

1. A doctor blade for differentially creping a flexible web from amoving surface and comprising a flexible sheet material doctor bladestrip having one longitudinal and continuous sharpened edge and a seriesof notches spaced apart on said longitudinal edge extending through thethickness of the sharpened edge, wherein the angle b formed by thebottom of said notches with respect to the base surface (23d) of saidblade strip (as illustrated in FIG. 6 of the drawings) is between about55 and 120, and the angle formed by blade surface (23a) and base surface(232]) is an acute angle between about 10 to 45.

References Cited UNITED STATES PATENTS 670,401 3/1901 Greth 1622811,588,732 6/1926 Hoberg 162281 2,995,180 8/1961 Klenk 264283 HOWARD R.CAINE, Primary Examiner US. Cl. X.R.

